Nanoplating of functional plasmonic gold and silver films

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Metal nanoparticles are known for their unique optical properties, such as their interaction with visible light or near-infrared radiation due to the excitation of localized surface plasmons. The plasmon resonance conditions strongly depend on the local chemical environment of the nanoparticles. For instance, the adsorption of molecules on the surface of a nanoparticle can alter the refractive index of its surrounding medium, causing a change in the nanoparticle-light interaction, which enables the optical detection of such processes. Based on this principle, optical sensors can be prepared, which can detect biomolecules rapidly, selectively and in trace amounts. Accordingly, plasmonic detection elements are promising components for a next generation of efficient biosensors, with important implications for medical diagnostics.This research proposal aims at demonstrating the potential of the electroless plating technique to synthesize gold and silver nanoparticle coatings for optical biosensing. Novel facile and versatile strategies for the deposition of nanoparticle films exhibiting localized surface plasmon resonance are in high demand, and electroless plating displays a promising wet-chemical option for this task: The method is simple, easily scalable, flexible regarding the substrate shape and material, and allows to widely adjust the functional properties of the deposited material.Traditionally, electroless plating is employed to fabricate closed metal films. Within the outlined project, the nanoscale control of electroless gold and silver plating will be enhanced to enable the production of well-defined nanoparticulate coatings. To this end, the involved seeding and plating reactions will be mutually optimized. Based on a systematic evaluation of the reaction parameters, strategies will be developed to control the density, size and shape of the resulting nanoparticles. Aside from ex situ morphological and compositional characterization, the plasmon resonance of the films will be analyzed by in situ spectroscopy in the course of their growth. The correlation between structural and optical evolution will be utilized to develop real-time controlled plating processes for nanoparticle films tailored toward the specific functional needs of plasmonic biosensing. Finally, selected nanoparticle coatings will be decorated with receptor molecules for the selective binding of biological analytes according to the key-lock-principle. This interaction will be used to investigate the biosensing performance of optimized systems.